The intended endpoint for Magnox Electric plc's reactor decommissioning strategy
is site clearance and de-licensing, which may require remediation of any 137CS
contaminated land on these sites. Phytoextraction might provide a practical and
environmentally acceptable method of reducing radioactive waste volumes for
disposal. Field trials conducted at Bradwell Nuclear Power Station, Essex, UK and
experiments in controlled conditions, using Beta vulgaris, showed that soil-to-plant
transfer factors increase as soil 137CS activity concentration decreases, implying that
constant 137CS removal rates are possible during site remediation. It was shown that
133CS might be responsible for this effect. Short time-interval multiple croppings
were not found to increase the rate of 137 Cs removal. For successful implementation
of 137CS phytoextraction plant species need to be identified that can accumulate
higher concentrations of 137 Cs than those identified at present. The large variation in
137CS uptake between species tested here suggests that extensive species screening
programmes will be required. Soil amendments appear essential to the
phytoextraction of aged 137CS and NH/, 133CS+ and K+ were shown to be capable of
extracting up to 25 % of the 137CS from soil at a field site. In a 14 month simulated
137CS phytoextraction trial in controlled conditions, over 60 % of 137CS applied to an
organic soil was removed using a 20 mg kg-1 CsCl soil amendment suggesting that,
where 137CS is sufficiently plant available, phytoextraction might be a useful soil
remediation technology. In a desk based BPEO study, composting was identified as
the most appropriate option for conditioning the biomass arising from 137 Cs
phytoextraction allowing it to be stored at the UK's LLW repository at Drigg,
Cumbria. It was concluded that the risk associated with soil amendments of 137 Cs
leaching off sites and the poor plant growth conditions likely to be found at field
sites would require the use of a greenhouse with soil contained in lysimeters during
phytoextraction.